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Title
Abstract
Figures
Introduction
Materials and Methods
Results
Discussion
Measured Data Computed
Implications for Podzolization Theory
Conclusions
References

Cornelis et al. 2014 Geoderma

Profile image of Jean-Thomas CornelisJean-Thomas Cornelis
https://doi.org/10.1016/J.GEODERMA.2014.06.023
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Abstract
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This study examines the processes involved in the formation and evolution of secondary minerals in soil, emphasizing their role in soil fertility and the global carbon budget. It explores how various environmental factors influence clay mineralogy across different soil ages in a chronosequence at Cox Bay. Key findings reveal significant isotopic changes in the clay-sized fraction associated with soil weathering and pedogenesis, contributing to a deeper understanding of chemical element cycling in soils.

Figures (9)
Fig. 1. Cross section of the Cox Bay study area showing site locations and soil horizons, depending on their respective age of soil formation: CB-0 year, CB-120 years, CB-175 years CB-270 years and CB-335 years.
Fig. 1. Cross section of the Cox Bay study area showing site locations and soil horizons, depending on their respective age of soil formation: CB-0 year, CB-120 years, CB-175 years CB-270 years and CB-335 years.
Nd = not determined. * Dithionite- (g-,), oxalate- (,,) and pyrophosphate- (,) extractable contents of Fe, Al and § > Total organic carbon. Summary of the major soil physical and chemical characteristics (for the fine earth <2 mm and the clay fraction <2 jm) of the investigated soils.
Nd = not determined. * Dithionite- (g-,), oxalate- (,,) and pyrophosphate- (,) extractable contents of Fe, Al and § > Total organic carbon. Summary of the major soil physical and chemical characteristics (for the fine earth <2 mm and the clay fraction <2 jm) of the investigated soils.
Fig. 2. XRD patterns of the clay-sized fraction (<2 um) of soils of the Cox Bay soil chronosequence after six treatments: K-saturation followed by drying at 20, 105, 300 and 550 °C, and Mg saturation followed by drying at 20 °C and saturation with ethylene-glycol. (A) CB-175 years E horizon, (B) CB-270 years E horizon, (C) CB-335 years E horizon, (D) CB-335 years BI horizon. Spacings of major reflections are in nanometers.
Fig. 2. XRD patterns of the clay-sized fraction (<2 um) of soils of the Cox Bay soil chronosequence after six treatments: K-saturation followed by drying at 20, 105, 300 and 550 °C, and Mg saturation followed by drying at 20 °C and saturation with ethylene-glycol. (A) CB-175 years E horizon, (B) CB-270 years E horizon, (C) CB-335 years E horizon, (D) CB-335 years BI horizon. Spacings of major reflections are in nanometers.
Fig. 3. Quantitative evolution of the mineralogy in the clay-sized fraction of the Cox Bay soil chronosequence. The clay-size mineralogy is comprised of primary minerals (quartz and amphiboles) and pedogenic clay minerals (kaolinite and 2:1 minerals). Chlorite, vermiculite, smectite, illite and mixed-layer minerals (MLM) are the 2:1 aluminosilicates encountered in the podzolic chronosequence.
Fig. 3. Quantitative evolution of the mineralogy in the clay-sized fraction of the Cox Bay soil chronosequence. The clay-size mineralogy is comprised of primary minerals (quartz and amphiboles) and pedogenic clay minerals (kaolinite and 2:1 minerals). Chlorite, vermiculite, smectite, illite and mixed-layer minerals (MLM) are the 2:1 aluminosilicates encountered in the podzolic chronosequence.
Fig. 4. Silicon isotopic signature (8°°Si %0; mean values -+ standard deviation represented by error bars) in the clay-sized fraction depending on soil ages and in primary lithogenic mineral: in the beach sand parental material. (A): 0- and 120-year-old soil fraction (8*°Si of primary minerals in beach sand in black and 5°°Si of the clay fraction of the 120-year-old BC horizon ir blue), (B): 175- and 270-year-old clay fractions (175 years = red A; 270 years = green 9), (C): 335-year-old clay fraction (purple O), and (D): clay fraction in an undated Belgian Podzo! (brown (). After only 175 years (B), we observe the depletion in light 7°Si in the clay fraction of the eluvial E horizon and enrichment in light 7°Si in the clay fraction of deeper illuvial soi horizon; respectively, relative depletion in light 78Si (+ 0.20%.) and relative enrichment in light 78Si (— 0.17%.) compared to the original Si isotopic signature of the unweathered clay frac- tion in the BC horizon. The isotopic fractionation increases over time with an enrichment in heavy *°Si of +0.42%. in the clay fraction of the E horizon and a concomitant enrichment in light ?8Si of — 0.32%. in the clay fraction of the Bhs horizon (after 335 years). We observe exactly the same tendency in the Belgian Podzol with enrichment in light 78Si in the clay fraction of the Bhs horizon of — 0.27%. compared to the unweathered clay fraction in BC horizon. (For interpretation of the references to color in this figure legend, the reader is referred to the web ver- sion of this article.)
Fig. 4. Silicon isotopic signature (8°°Si %0; mean values -+ standard deviation represented by error bars) in the clay-sized fraction depending on soil ages and in primary lithogenic mineral: in the beach sand parental material. (A): 0- and 120-year-old soil fraction (8*°Si of primary minerals in beach sand in black and 5°°Si of the clay fraction of the 120-year-old BC horizon ir blue), (B): 175- and 270-year-old clay fractions (175 years = red A; 270 years = green 9), (C): 335-year-old clay fraction (purple O), and (D): clay fraction in an undated Belgian Podzo! (brown (). After only 175 years (B), we observe the depletion in light 7°Si in the clay fraction of the eluvial E horizon and enrichment in light 7°Si in the clay fraction of deeper illuvial soi horizon; respectively, relative depletion in light 78Si (+ 0.20%.) and relative enrichment in light 78Si (— 0.17%.) compared to the original Si isotopic signature of the unweathered clay frac- tion in the BC horizon. The isotopic fractionation increases over time with an enrichment in heavy *°Si of +0.42%. in the clay fraction of the E horizon and a concomitant enrichment in light ?8Si of — 0.32%. in the clay fraction of the Bhs horizon (after 335 years). We observe exactly the same tendency in the Belgian Podzol with enrichment in light 78Si in the clay fraction of the Bhs horizon of — 0.27%. compared to the unweathered clay fraction in BC horizon. (For interpretation of the references to color in this figure legend, the reader is referred to the web ver- sion of this article.)
* Mineralogy of the clay fraction quantified using the Siroquant software V4.0; primary minerals = quartz + amphiboles; secondary minerals = kaolinite + 2:1 minerals (vermiculite, smectite, illite, chlorite, mixed-layers minerals). > The 6°°Si of secondary minerals present in the clay fraction is computed as follows: 8°°Simin n = ((8°°Siciay fraction — % Min I * 8°°Sinin 1) / % min II), where min I = primary minerals, min II = secondary minerals and 8°°Sinin 1 = —0.27%o. © Si isotope discrimination between “unweathered” clay minerals in BC horizon and pedogenic clay minerals in the “x” horizon of interest (x = E, Bh or Bhs horizons): 5?°Sig-8?°Sigc or §°Sig-—-8°Sign Bhs. Quantification of primary and secondary minerals in the clay-sized fraction of the Cox Bay soil chronosequence. The clay-sized quantification is then used for the Si isotopic mass balanc approach.
* Mineralogy of the clay fraction quantified using the Siroquant software V4.0; primary minerals = quartz + amphiboles; secondary minerals = kaolinite + 2:1 minerals (vermiculite, smectite, illite, chlorite, mixed-layers minerals). > The 6°°Si of secondary minerals present in the clay fraction is computed as follows: 8°°Simin n = ((8°°Siciay fraction — % Min I * 8°°Sinin 1) / % min II), where min I = primary minerals, min II = secondary minerals and 8°°Sinin 1 = —0.27%o. © Si isotope discrimination between “unweathered” clay minerals in BC horizon and pedogenic clay minerals in the “x” horizon of interest (x = E, Bh or Bhs horizons): 5?°Sig-8?°Sigc or §°Sig-—-8°Sign Bhs. Quantification of primary and secondary minerals in the clay-sized fraction of the Cox Bay soil chronosequence. The clay-sized quantification is then used for the Si isotopic mass balanc approach.
Fig. 5. Evolution of Si isotope composition with elemental composition (Si, Al, Ge) and the proportion of poorly crystalline Si (Sipx/Siday) in the clay fraction for the Cox Bay soil chronosequence (175-year-old soil = red A; 270-year-old soil = green ¢; 335-year-old soil = purple O) and for the Gaume Podzol (brown (1). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
Fig. 5. Evolution of Si isotope composition with elemental composition (Si, Al, Ge) and the proportion of poorly crystalline Si (Sipx/Siday) in the clay fraction for the Cox Bay soil chronosequence (175-year-old soil = red A; 270-year-old soil = green ¢; 335-year-old soil = purple O) and for the Gaume Podzol (brown (1). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
Fig. 6. Conceptual representation of the contribution of Si released from the dissolution of primary and secondary Si pools (lithogenic, biogenic and pedogenic) to the re-precipitation o new “tertiary” clay minerals during podzolization. Phase I > phase II (C > BC) = transition from the parent C material to the pedogenic BC horizon with neoformation of secondary cla\ minerals. Phase II = formation of typical podzolic soil horizons: E, Bh, Bhs, Bs and Bw. Phase II > phase III = transition from young to older Podzol characterized by (i) the deepening o the E horizon where secondary clay minerals are weathered and enriched in heavy *°Si (Ey — Ey), and (ii) B horizons tertiary clay minerals re-precipitate and are enriched in light 7°Si (BC, — Bhsyq).
Fig. 6. Conceptual representation of the contribution of Si released from the dissolution of primary and secondary Si pools (lithogenic, biogenic and pedogenic) to the re-precipitation o new “tertiary” clay minerals during podzolization. Phase I > phase II (C > BC) = transition from the parent C material to the pedogenic BC horizon with neoformation of secondary cla\ minerals. Phase II = formation of typical podzolic soil horizons: E, Bh, Bhs, Bs and Bw. Phase II > phase III = transition from young to older Podzol characterized by (i) the deepening o the E horizon where secondary clay minerals are weathered and enriched in heavy *°Si (Ey — Ey), and (ii) B horizons tertiary clay minerals re-precipitate and are enriched in light 7°Si (BC, — Bhsyq).

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New Zealand Journal of Agricultural Research, 2018

Using data from the literature, we pose the question of the extent to which a knowledge of soils is contributed by that of its clay fraction. In the past, soil characteristics have not related well to mineralogical analyses but we have redefined clays and also used a computer programme to more closely analyse X-ray diffraction (XRD) profiles. It was found that cation exchange capacities and specific surface areas of soil kaolinites almost always exceed those of standard kaolinites. The surfaces of soil clays are often coated by organic matter, which reduces their capacity to adsorb dissolved organic carbon (DOC). Oxidised iron is closely associated with phyllosilicate clays and enhances their capacity to adsorb DOC. Computer-aided decomposition of XRD traces show that phyllosilicates may contain several phases and react dynamically with potassium-containing solutions. Clays should be regarded as natural products with as yet undiscovered applications, including for cancer treatment.

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Carbon Stabilization by Clays in the Environment
guixue Song

Carbon Stabilization by Clays in the Environment, 2009

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Dynamic role of “illite-like” clay minerals in temperate soils: facts and hypotheses
Luc Abbadie, Bruce Velde

Biogeochemistry, 2007

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Landscape cultivation alters δ(30)Si signature in terrestrial ecosystems
Jean-Thomas Cornelis, Eric Struyf

Scientific reports, 2015

Despite increasing recognition of the relevance of biological cycling for Si cycling in ecosystems and for Si export from soils to fluvial systems, effects of human cultivation on the Si cycle are still relatively understudied. Here we examined stable Si isotope (δ(30)Si) signatures in soil water samples across a temperate land use gradient. We show that - independent of geological and climatological variation - there is a depletion in light isotopes in soil water of intensive croplands and managed grasslands relative to native forests. Furthermore, our data suggest a divergence in δ(30)Si signatures along the land use change gradient, highlighting the imprint of vegetation cover, human cultivation and intensity of disturbance on δ(30)Si patterns, on top of more conventionally acknowledged drivers (i.e. mineralogy and climate).

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Silicon isotopes in Arctic and sub-Arctic glacial meltwaters: the role of subglacial weathering in the silicon cycle
Jakub D Zarsky

Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences

Glacial environments play an important role in high-latitude marine nutrient cycling, potentially contributing significant fluxes of silicon (Si) to the polar oceans, either as dissolved silicon (DSi) or as dissolvable amorphous silica (ASi). Silicon is a key nutrient in promoting marine primary productivity, contributing to atmospheric CO 2 removal. We present the current understanding of Si cycling in glacial systems, focusing on the Si isotope (δ 30 Si) composition of glacial meltwaters. We combine existing glacial δ 30 Si data with new measurements from 20 sub-Arctic glaciers, showing that glacial meltwaters consistently export isotopically light DSi compared with non-glacial rivers (+0.16‰ versus +1.38‰). Glacial δ 30 Si ASi composition ranges from −0.05‰ to −0.86‰ but exhibits low seasonal variability. Silicon fluxes and δ 30 Si composition from glacial systems are not commonly included in global Si budgets and isotopic mass balance calculations at present. We discuss outstand...

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The silicon isotope composition of Ethmodiscus rex laminated diatom mats from the tropical West Pacific: Implications for silicate cycling during the Last Glacial Maximum
Thomas Algeo

Paleoceanography, 2015

The cause of massive blooms of Ethmodiscus rex laminated diatom mats (LDMs) in the eastern Philippine Sea (EPS) during the Last Glacial Maximum (LGM) remains uncertain. In order to better understand the mechanism of formation of E. rex LDMs from the perspective of dissolved silicon (DSi) utilization, we determined the silicon isotopic composition of single E. rex diatom frustules (δ 30 Si E. rex) from two sediment cores in the Parece Vela Basin of the EPS. In the study cores, δ 30 Si E. rex varies from À1.23‰ to À0.83‰ (average À1.04‰), a range that is atypical of marine diatom δ 30 Si and that corresponds to the lower limit of reported diatom δ 30 Si values of any age. A binary mixing model (upwelled silicon versus eolian silicon) accounting for silicon isotopic fractionation during DSi uptake by diatoms was constructed. The binary mixing model demonstrates that E. rex dominantly utilized DSi from eolian sources (i.e., Asian dust) with only minor contributions from upwelled seawater sources (i.e., advected from Subantarctic Mode Water, Antarctic Intermediate Water, or North Pacific Intermediate Water). E. rex utilized only~24% of available DSi, indicating that surface waters of the EPS were eutrophic with respect to silicon during the LGM. Our results suggest that giant diatoms did not always use a buoyancy strategy to obtain nutrients from the deep nutrient pool, thus revising previously proposed models for the formation of E. rex LDMs.

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Patterning total mercury distribution in coastal podzolic soils from an Atlantic area: Influence of pedogenetic processes and soil components
Manuel Madeira

Catena, 2021

Soils are the main Hg reservoir in the terrestrial ecosystems where it is deposited via wet or dry deposition and litterfall. Once on the soil surface, different biogeochemical routes will determine the fate of Hg and the role of terrestrial ecosystems as a Hg source or sink. The specific chemical and physical characteristics of Podzols and podzolic soils contribute to the accumulation of Hg in their illuvial horizons, avoiding its leaching to groundwater. The geographical location, state of pedogenesis, soil age, abundance of carrier phases and physical properties can affect the presence and distribution of Hg in soils. Therefore, understand and relate these factors with the behavior of Hg in Podzols and podzolic soils is key to define the role of this type of soil in the terrestrial Hg cycle. In this work, ten podzolic soil profiles were collected in an Atlantic coastal forest area of Portugal and analyzed for the main physico-chemical properties and Hg content to assess the influ...

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Ge and Si Isotope Behavior During Intense Tropical Weathering and Ecosystem Cycling
Sophie Opfergelt

Global Biogeochemical Cycles, 2020

Chemical weathering of volcanic rocks in warm and humid climates contributes disproportionately to global solute fluxes. Geochemical signatures of solutes and solids formed during this process can help quantify and reconstruct weathering intensity in the past. Here, we measured silicon (Si) and germanium (Ge) isotope ratios of the soils, clays, and fluids from a tropical lowland rainforest in Costa Rica. The bulk topsoil is intensely weathered and isotopically light (mean ± 1σ: δ 30 Si ¼ −2.1 ± 0.3‰, δ 74 Ge ¼ −0.13 ± 0.12‰) compared to the parent rock (δ 30 Si ¼ −0.11 ± 0.05‰, δ 74 Ge ¼ 0.59 ± 0.07‰). Neoforming clays have even lower values (δ 30 Si ¼ −2.5 ± 0.2‰, δ 74 Ge ¼ −0.16 ± 0.09‰), demonstrating a whole-system isotopic shift in extremely weathered systems. The lowland streams represent mixing of dilute local fluids (δ 30 Si ¼ 0.2 − 0.6‰, δ 74 Ge ¼ 2.2 − 2.6‰) with solute-rich interbasin groundwater (δ 30 Si ¼ 1.0 ± 0.2‰, δ 74 Ge ¼ 4.0‰). Using a Ge-Si isotope mass balance model, we calculate that 91 ± 9% of Ge released via weathering of lowland soils is sequestered by neoforming clays, 9 ± 9% by vegetation, and only 0.2 ± 0.2% remains dissolved. Vegetation plays an important role in the Si cycle, directly sequestering 39 ± 14% of released Si and enhancing clay neoformation in surface soils via the addition of amorphous phytolith silica. Globally, volcanic soil δ 74 Ge closely tracks the depletion of Ge by chemical weathering (τ Ge), whereas δ 30 Si and Ge/Si both reflect the loss of Si (τ Si). Because of the different chemical mobilities of Ge and Si, a δ 74 Ge-δ 30 Si multiproxy system is sensitive to a wider range of weathering intensities than each isotopic system in isolation.

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